RE: [PATCH] xen-netback: fix occasional leak of grant ref mappings under memory pressure
From: Paul Durrant
Date: Thu Feb 28 2019 - 06:50:03 EST
> -----Original Message-----
> From: Igor Druzhinin [mailto:igor.druzhinin@xxxxxxxxxx]
> Sent: 28 February 2019 11:44
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; Wei Liu <wei.liu2@xxxxxxxxxx>
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> Subject: Re: [PATCH] xen-netback: fix occasional leak of grant ref mappings under memory pressure
> On 28/02/2019 11:21, Paul Durrant wrote:
> >>> @@ -1153,6 +1152,10 @@ static int xenvif_tx_submit(struct xenvif_queue *queue)
> >>> kfree_skb(skb);
> >>> continue;
> >>> }
> >>> +
> >>> + /* Copied all the bits from the frag list. */
> >>> + skb_frag_list_init(skb);
> >>> + kfree(nskb);
> >> I think you want kfree_skb here?
> > No. nskb is the frag list... it is unlinked from skb by the call to skb_frag_list_init() and then it
> can be freed on its own. The skb is what we need to retain, because that now contains all the data.
> Are you saying previous code in xenvif_handle_frag_list() incorrectly
> called kfree_skb()?
No, it correctly called kfree_skb() on nskb in the success case. What Wei and myself would prefer is that we have a single place that the frag list is freed in both the success and error cases.